Implement a new typeclass hierarchy (again) #64
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This will take me a while to look at (and needs rebasing now), but I release the non-breaking changes to Hackage in the meantime: https://hackage.haskell.org/package/product-profunctors-0.11.1.0 |
It represents "`SemiProductProfunctor` with a unit".
This places all three main ways of viewing this class on equal footing: * The "tupling profunctors" perspective: `p a b -> p a' b' -> p (a, a') (b, b')` * The "applicative output" perspective: `p x (a -> b) -> p x a -> p x b` * The "divisible input" perspective: `(a -> (b, c)) -> p b x -> p c x -> p a x`
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Rebased and pushed. TH is still broken, which breaks CI; I don't really want to wrangle TH until we agree on the interface again. |
| SemiproductProfunctor(..), | ||
| (***$), |
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Should probably explicitly export ProductProfunctor(..) and SumProfunctor(..) in their respective sections?
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| -- /Since 0.12.0.0:/ Superclass constraint relaxed from @'Monoid' r@ | ||
| -- to @'Semigroup' r@. |
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I don't know exactly how to word this but this probably isn't right.
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Have you had a chance to look at this? If you're happy with the new typeclass design and the decision to start using |
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Hello, sorry for the slow reply. This is on my TODO list but I'm only making progress on my list slowly ... |
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By the way, adding these new combinators (but not deprecating the old versions) is easy to add in the current major release of
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Having said that, I do need to think about how to do this in a way that makes the upgrade path as smooth as possible (unless you or I already did that, and I forgot about it). |
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OK, so after investigation:
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Rebuilding my take on the hierarchy hashed out at the end of the comment thread on #54 in a commit-by-commit branch
Defines:
Profunctor => SemiproductProfunctor => ProductProfunctor
This operates on tuples, and gives the operations from the
Applicative(Apply) and Divisible(Divise) typeclasses.
Profunctor => SemisumProfunctor => SumProfunctor
This operates on Eithers, and gives the operations from the
Decidable (Decide/Conclude) typeclasses.
Breaking changes:
purePP->purePfor consistency with everything else.purePPstill exists but is deprecated.empty->unitPfor consistency withvoidP.emptystill exists but is deprecated.(***!)moved toSemiproductProfunctor(+++!)moved toSemisumProfunctorOpen questions:
semigroupoids; finessing our typeclasses so there's a "has unit/no unit" split is significantly less useful unless we can write instances in terms ofApplyetc. If you agree, I will add a semigroupoids commit to this PR.Tests are currently busted because
makeAdaptorAndInstanceis completely busted, but I wanted to get eyes on this before I forget to look at it for another year.Needs to be rebased after #61, #62, and #63 all go out.Closes #54
Closes #59
Closes #50